Water-based asphalt-based carbon fiber wave-absorbing slurry, preparation method and application thereof
By modifying and optimizing the formulation of water-based asphalt-based carbon fiber absorbing slurry, the problems of uneven dispersion and insufficient low-frequency performance of carbon fiber slurry were solved, achieving a low-frequency broadband absorbing effect, which is suitable for military facility stealth and electromagnetic shielding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-09
AI Technical Summary
Existing low-frequency radar absorbing materials are difficult to achieve broadband absorption at a small thickness. The carbon fiber slurry is unevenly dispersed, and the low-frequency performance of PAN-based carbon fiber is insufficient, resulting in poor honeycomb absorption effect.
A water-based asphalt-based carbon fiber microwave absorbing slurry was used. By combining ozone and slurry treatment, the surface activity of the carbon fiber was improved. Combined with dopamine hydrochloride slurry agent, the slurry formulation and feeding sequence were optimized to achieve uniform dispersion of carbon fiber in a water-based carrier and prepare low-frequency broadband microwave absorbing honeycomb.
It achieves improved low-frequency broadband absorption performance with a smaller thickness. The prepared absorbing cell has a reflectivity of less than -10dB in the 1GHz~2GHz frequency band, which is suitable for industrial production and meets the stealth and electromagnetic shielding requirements of military facilities.
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Figure CN122167077A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electromagnetic absorbing materials technology, specifically relating to an aqueous asphalt-based carbon fiber absorbing slurry, its preparation method and application. It also discloses a process for preparing low-frequency, broadband absorbing honeycomb using this slurry, which can be applied to fields such as military facility stealth, electromagnetic shielding and protection. Background Technology
[0002] Electromagnetic wave absorbing materials can convert electromagnetic energy in specific wavebands or weaken the electromagnetic properties of targets through interference cancellation, making them a key technology for military stealth. Honeycomb absorbing structures are made by preparing blank honeycomb core materials based on aramid paper and impregnating them with absorbing slurry. They combine the advantages of lightweight, high strength, and high electromagnetic loss, and have been applied to stealth equipment such as the F-117 and B-2.
[0003] Currently, the technology for mid-to-high frequency radar absorbing materials is mature, but the development of low-frequency detection technology has made L-band (1-2GHz) absorption a technical challenge: according to the quarter-wavelength theory, the matching thickness of low-frequency absorbing materials is much higher than that for centimeter / millimeter waves; magnetic low-frequency absorbing agents such as ferrite and carbonyl iron have high densities and are not suitable for cellular loading. Existing low-frequency absorbing schemes mainly fall into two categories: constructing artificial periodic macroscopic structures and developing new low-frequency absorbing materials.
[0004] Carbon fiber, as a carbon-based microwave absorbing material, possesses advantages such as low density, good conductivity, and no additional magnetic field interference. The aspect ratio of its one-dimensional structure directly affects its electromagnetic response characteristics. Carbon fibers with a large aspect ratio, possessing low-excitation-energy electrons and long electron transport orbitals, are potential preferred materials for low-frequency microwave absorption. However, significant problems exist in the application of carbon fiber: its surface inertness and lack of oxygen-containing groups lead to poor bonding with resins and easy agglomeration; the large density difference with the solvent causes long carbon fibers to easily settle, resulting in uneven slurry dispersion and difficulty in loading onto the honeycomb sidewalls, leading to ineffective microwave absorption in the prepared honeycomb. Currently, carbon fiber modification technology mainly focuses on PAN-based carbon fibers, with limited research on the modification of pitch-based carbon fibers. Furthermore, commonly used PAN-based carbon fibers lack sufficient orientation and crystallinity, resulting in insignificant low-frequency (L-band) microwave absorption characteristics, necessitating the development of novel low-frequency microwave absorbing materials. Summary of the Invention
[0005] To address the problems in existing technologies such as the inability of absorbing honeycomb to achieve low-frequency broadband absorption at relatively small thicknesses, poor dispersion stability of carbon fiber slurry, and insufficient low-frequency performance of PAN-based carbon fiber, this invention provides an aqueous asphalt-based carbon fiber absorbing slurry, its preparation method, and its application. Through combined ozone and slurry treatment, uniform and stable dispersion of the absorbing slurry is achieved. This slurry can be used in the preparation of absorbing honeycomb, improving the low-frequency broadband absorption performance of the honeycomb and meeting the needs of practical production applications.
[0006] A water-based asphalt-based carbon fiber microwave absorbing slurry is composed of a carrier, a microwave absorbing agent, and additives.
[0007] The carrier is an aqueous organosilicon resin, the microwave absorber is pitch-based carbon fiber, and the additives include anti-settling agent, dispersant, and sizing agent. The microwave absorber is dispersed in the carrier to obtain a microwave absorbing slurry; the sizing agent is dopamine hydrochloride.
[0008] The components are proportioned as follows by mass ratio / parts: the mass ratio of pitch-based carbon fiber to water-based silicone resin is 13%~32%; deionized water is 150%~200% of the total mass of pitch-based carbon fiber and silicone resin; anti-settling agent is 0.15%~0.3% of the total mass of deionized water, silicone resin and pitch-based carbon fiber; dispersant is 0.2%~1% of the total mass of deionized water, silicone resin and pitch-based carbon fiber; sizing agent is 3%~10% of the mass of pitch-based carbon fiber.
[0009] Furthermore, the water-based silicone resin (adhesive) contains 13-32 parts, the microwave absorber (pitch-based carbon fiber) contains 4-9 parts, the water contains 26-51 parts, the dispersant contains 0.2-0.5 parts, the anti-settling agent contains 0.1-0.2 parts, and the sizing agent contains 0.2-0.45 parts.
[0010] Furthermore, the length of the pitch-based carbon fiber is preferably 30~50μm.
[0011] Furthermore, the dispersant is one or more of sodium dodecyl sulfate, polyethylene glycol, Triton, and Tween.
[0012] Furthermore, the anti-settling agent is one or more of methylcellulose, carboxymethylcellulose, and sodium carboxymethylcellulose.
[0013] A method for preparing water-based bitumen-based carbon fiber microwave absorbing slurry
[0014] Step 1: Weigh the raw materials according to the formula: pitch-based carbon fiber, water-based silicone resin, deionized water, dispersant, anti-settling agent, and dopamine hydrochloride.
[0015] Step 2, Ozone modification of pitch-based carbon fiber surface: Ozone is used to clean the surface of pitch-based carbon fiber, introducing active sites and improving the subsequent bonding ability with sizing agent.
[0016] Step 3, Sizing treatment of pitch-based carbon fiber: Put 4-9 parts of pitch-based carbon fiber into 26-51 parts of deionized water, add 0.2-0.45 parts of dopamine hydrochloride, and treat with ultrasonic waves at 400-800w for 10-30 minutes to obtain a mixture.
[0017] Step 4: Mechanical stirring of the mixture: The mixture obtained in step 3 is mechanically stirred at a speed of 300-600 r / min for 0.5-1 h to achieve uniform mixing of pitch-based carbon fiber and sizing agent.
[0018] Step 5: Vacuum drying to prepare sized pitch-based carbon fiber: Place the uniformly dispersed mixture from step 4 into a vacuum drying oven and vacuum dry at 40-60℃ until completely dry to obtain the modified sized pitch-based carbon fiber for later use.
[0019] Step 6, Solvent modification: Add deionized water to the container and mechanically stir at a speed of 300~600 r / min. While stirring, add the dispersant and continue stirring for at least 5 minutes to obtain a solvent with low surface energy, thereby improving the wetting properties of the microwave absorber.
[0020] Step 7: Prepare carbon slurry: While stirring (300~600r / min), add the sizing pitch-based carbon fiber obtained in step 5 to the modified solvent obtained in step 6, and stir for at least 10min to prevent the pitch-based carbon fiber from agglomerating, so as to obtain a uniform carbon slurry.
[0021] Step 8: Preparation of microwave absorbing slurry: Add water-based organosilicon resin to the carbon slurry obtained in step 7, and add anti-settling agent while stirring. Adjust the slurry viscosity to 40~60cps, and continue stirring for at least 10 minutes until the mixture is uniform to obtain the final water-based asphalt-based carbon fiber microwave absorbing slurry.
[0022] The above-mentioned water-based asphalt-based carbon fiber absorbing slurry is used as an absorbing slurry for absorbing honeycomb structures.
[0023] In summary, this invention uses highly conductive pitch-based carbon fiber as a microwave absorber. Pitch-based carbon fiber contains a large number of low-excitation-energy free electrons and exhibits superior orientation and crystallinity compared to PAN-based carbon fiber, achieving a breakthrough in low-frequency microwave absorption from the material's fundamental nature and solving the problem of insufficient low-frequency performance of ordinary PAN-based carbon fiber. Simultaneously, ozone treatment introduces active sites on the surface of the pitch-based carbon fiber, enhancing the bonding between dopamine hydrochloride and the pitch-based carbon fiber. The dopamine sizing agent reduces the surface roughness and Coulomb friction of the pitch-based carbon fiber while introducing hydrogen bonds to improve hydrophilicity, completely solving the problems of agglomeration and sedimentation of pitch-based carbon fiber. Furthermore, the optimized feeding sequence—adding a dispersant first to reduce solvent surface tension and then adding an anti-settling agent last to regulate viscosity—avoids the high power and high cost issues associated with mechanical dispersion at high viscosity, achieving uniform and stable dispersion of carbon fiber in an aqueous carrier, facilitating loading on the honeycomb sidewalls. Attached Figure Description
[0024] Figure 1 This is a comparison chart of carbon fiber properties;
[0025] Figure 2 Flowchart of carbon fiber sizing process;
[0026] Figure 3 This is an image showing the effect of sizing carbon fiber;
[0027] Figure 4This is a flowchart illustrating the fabrication process of the absorbing cell in an example.
[0028] Figure 5 The reflectance curve of the honeycomb prepared for the example;
[0029] Figure 6 The gradient design effect of the honeycomb structure fabricated in the example;
[0030] Figure 7 The low-frequency dielectric parameters of the honeycomb fabricated in the example are shown.
[0031] Figure 8 The low-frequency reflectivity of the honeycomb fabricated in the example is shown. Detailed Implementation
[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, and the effectiveness and absorption performance of the present invention will be verified.
[0033] In this embodiment, the microwave absorber is pitch-based carbon fiber, such as... Figure 1 As shown, the difference in electrical conductivity between pitch-based carbon fiber and ordinary PAN-based carbon fiber is demonstrated, proving the electrical performance advantages of pitch-based carbon fiber.
[0034] The carbon fiber sizing process in this embodiment is as follows: Figure 2 As shown, the entire process of carbon fiber modification—including ozone treatment, dopamine mixing, ultrasonication, stirring, and vacuum drying—is clearly demonstrated. Specifically, after weighing the raw materials according to the specified proportions, the carbon fibers were treated in a 1500W UV ozone generator for 10 minutes to oxidize the surface. Then, deionized water and dopamine hydrochloride (5% of the carbon fiber mass) were added. The sizing agent and carbon fibers were initially mixed using an ultrasonic cleaner for 30 minutes. Afterward, mechanical stirring was performed at 300 rpm for 30 minutes until a uniform mixture was obtained. Finally, vacuum drying was carried out at 0.05 MPa, a drying temperature of 60℃, and a drying time of 24 hours. The sizing carbon fibers were obtained, and the sizing effect was as shown. Figure 3 As shown, the dispersion state and surface characteristics of the modified sized carbon fibers are intuitively presented, and sizing can significantly introduce oxygen-containing sites.
[0035] A method for preparing a water-based asphalt-based carbon fiber radar absorbing honeycomb, such as... Figure 4 As shown, the specific steps are as follows:
[0036] S1. Solvent Modification: Weigh 8057 parts of water, and add 67 parts of sodium dodecyl sulfate while stirring at a speed of 300 r / min for 5 min. Allow the dispersant to dissolve completely to obtain solution 1.
[0037] S2. Carbon paste preparation: Weigh 800 parts of sized carbon fiber and add it to solution 1 while stirring. The stirring speed is 300 r / min and the stirring time is 10 min to obtain a uniformly distributed carbon paste.
[0038] S3. Preparation of the microwave absorbing slurry: Add 4571 parts of silicone resin to the carbon slurry, stir at 300 r / min for 20 min, and after thorough dispersion, add 26 parts of methylcellulose in batches. Specifically, sieve the slurry through a screen, with no more than 5g added at a time. If a large dose of methylcellulose is added at once, the outer layer will dissolve and cross-link, coating the inner methylcellulose, making it difficult to dissolve and causing it to agglomerate and settle, and it will not be dispersed by mechanical stirring. The solution viscosity should be 40~60 cps. If the viscosity is too high, blowing will be difficult, requiring a long time to reach the ideal weight gain. If the viscosity is too low, the slurry will have weak bonding with the aramid honeycomb, resulting in less material adhering and high fluidity, causing it to settle to the bottom of the honeycomb under gravity.
[0039] S4. Honeycomb Impregnation: Place a 300*300*10mm aramid paper honeycomb on top of the slurry and allow it to sink freely to the support frame (20mm). The impregnation time is fixed at 1 minute, and the impregnation temperature is controlled at 24℃. Aramid paper honeycomb with a dielectric real part of 2.3, a loss tangent of 0.001, a pore size of 1.8mm, and a density of 48kg / m³ is selected.
[0040] S5. Air Knife Purging: Place the impregnated honeycomb on a special air knife with a height of 40mm and an air pressure of 0.3Mpa, and purge until the wet weight density reaches 22kg / m³. Each time the air knife passes over the honeycomb, it flips the honeycomb over and rotates it horizontally by 90° to prevent the slurry from accumulating at the bottom under the action of wind and gravity.
[0041] S6. Curing and Baking: Place the impregnated honeycomb in an oven for curing and baking at a temperature of 120℃~180℃. The baking time at 120℃ is 30 minutes, followed by curing at 180℃ for 1-6 hours to increase the bonding between the slurry and the aramid honeycomb. This yields pitch-based carbon fiber microwave absorbing honeycomb.
[0042] Figure 5 The reflectance curves of the cellular cell obtained in this embodiment show the reflectance variations and effective absorption frequency bands in the mid-to-high frequency range under TE and TM polarization. Mid-to-high frequency absorption performance: The finished cellular cell exhibits reflectance less than -10dB in the 4.12GHz~9.72GHz frequency band under TE polarization and in the 3.84GHz~8.60GHz frequency band under TM polarization, demonstrating excellent mid-to-high frequency absorption performance. Further, impedance matching optimization can be performed by impregnating to different heights to extend the bandwidth, such as... Figure 6 As shown, two polarizations can be achieved in broadband speeds of 2-18 GHz.
[0043] To verify the low-frequency performance, we tested the low-frequency dielectric properties of the cellular battery, with dielectric parameters ranging from 0.3 GHz to 2 GHz as follows: Figure 7 As shown, the feeding weight is controlled by controlling the number of impregnation cycles, and the low-frequency absorption effect is calculated using transmission line theory. Figure 8 As shown, at a thickness of 35mm, the reflectivity is less than -10dB in the 1GHz~2GHz frequency band. This demonstrates excellent low-frequency absorption capability.
[0044] As can be seen from the above embodiments, the present invention:
[0045] Pitch-based carbon fiber is selected as the microwave absorbing agent. Compared with PAN-based carbon fiber, it has better conductivity and a large number of low-excitation-energy free electrons, thus achieving the advantage of low-frequency microwave absorption from the material level.
[0046] By employing ozone surface modification combined with dopamine hydrochloride sizing technology, active sites are introduced onto the carbon fiber surface to enhance its hydrophilicity and binding force with the carrier, thereby solving the problems of carbon fiber agglomeration and sedimentation.
[0047] By optimizing the slurry formulation and feeding sequence, a dispersant is added first to reduce the solvent surface energy, and an anti-settling agent is added last to regulate the viscosity, significantly improving the dispersion stability of the slurry. By precisely controlling the carbon fiber volume fraction, honeycomb impregnation height, and feeding weight gain, broadband high-efficiency impedance matching and electromagnetic wave energy dissipation are achieved.
[0048] Using water-based silicone resin as a carrier, combined with anti-settling agents and dispersants to form an water-based slurry system, which is suitable for the impregnation process of aramid paper honeycomb, the prepared absorbing honeycomb has excellent wave absorption performance in the low frequency band, and the process is simple and suitable for industrial production.
[0049] Excellent absorption performance: The prepared absorbing cell exhibits a reflectivity of less than -10dB in the 4.12GHz~9.72GHz frequency band under TE polarization; less than -10dB in the 3.84GHz~8.60GHz frequency band under TM polarization; and less than -10dB in the 1GHz~2GHz low-frequency band with a thickness of 35mm. Full-bandwidth absorption of 2~18GHz can be achieved through impregnation height optimization, meeting the requirements for low-frequency broadband absorption.
[0050] High process adaptability: It uses water-based silicone resin as a carrier to form a water-based slurry system, which is highly compatible with the aramid paper honeycomb impregnation process; the parameters during the preparation process are controllable, and steps such as air knife blowing, curing and baking can be easily industrialized, making it suitable for actual production applications.
[0051] Excellent overall performance: The absorbing honeycomb retains the inherent advantages of aramid honeycomb in terms of light weight and high strength. It has no additional magnetic field and will not cause electromagnetic interference to the equipment. It has the dual functions of electromagnetic absorption and structural support, making it suitable for high-end application scenarios such as military equipment.
Claims
1. A water-based asphalt-based carbon fiber microwave absorbing slurry, comprising a carrier, a microwave absorbing agent, and additives, characterized in that: The carrier is a water-based silicone resin, the microwave absorber is pitch-based carbon fiber, and the additives include anti-settling agents, dispersants, and sizing agents. The microwave absorber is dispersed in the carrier to obtain a microwave absorbing slurry; the sizing agent is dopamine hydrochloride. The components are proportioned as follows by mass ratio / parts: the mass ratio of pitch-based carbon fiber to water-based silicone resin is 13%~32%; deionized water is 150%~200% of the total mass of pitch-based carbon fiber and silicone resin; anti-settling agent is 0.15%~0.3% of the total mass of deionized water, silicone resin and pitch-based carbon fiber; dispersant is 0.2%~1% of the total mass of deionized water, silicone resin and pitch-based carbon fiber; sizing agent is 3%~10% of the mass of pitch-based carbon fiber.
2. The water-based bitumen-based carbon fiber microwave absorbing slurry as described in claim 1, characterized in that: The composition includes 13-32 parts of water-based silicone resin, 4-9 parts of pitch-based carbon fiber, 26-51 parts of water, 0.2-0.5 parts of dispersant, 0.1-0.2 parts of anti-settling agent, and 0.2-0.45 parts of sizing agent.
3. The water-based bitumen-based carbon fiber microwave absorbing slurry as described in claim 1, characterized in that: The preferred length of the pitch-based carbon fiber is 30~50μm.
4. The water-based bitumen-based carbon fiber microwave absorbing slurry as described in claim 1, characterized in that: The dispersant is one or more of sodium dodecyl sulfate, polyethylene glycol, Triton, and Tween.
5. The water-based bitumen-based carbon fiber microwave absorbing slurry as described in claim 1, characterized in that: The anti-settling agent is one or more of methylcellulose, carboxymethylcellulose, and sodium carboxymethylcellulose.
6. The method for preparing the water-based bitumen-based carbon fiber microwave absorbing slurry as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Weigh the raw materials according to the formula: pitch-based carbon fiber, water-based silicone resin, deionized water, dispersant, anti-settling agent, and dopamine hydrochloride; Step 2, Ozone modification of pitch-based carbon fiber surface: Ozone is used to clean the surface of pitch-based carbon fiber to introduce active sites; Step 3, Sizing treatment of pitch-based carbon fiber: Put 4-9 parts of pitch-based carbon fiber into 26-51 parts of deionized water, add 0.2-0.45 parts of dopamine hydrochloride, and treat with ultrasonic waves at 400-800w for 10-30 minutes to obtain a mixture. Step 4: Mechanical stirring of the mixture: The mixture obtained in Step 3 is mechanically stirred at a speed of 300-600 r / min for 0.5-1 h to achieve uniform mixing of pitch-based carbon fiber and sizing agent. Step 5: Vacuum drying to prepare sized pitch-based carbon fiber: Place the uniformly dispersed mixture from step 4 into a vacuum drying oven and vacuum dry at 40-60℃ until completely dry to obtain the modified sized pitch-based carbon fiber for later use. Step 6, Solvent modification: Add deionized water to the container and mechanically stir at a speed of 300~600 r / min. While stirring, add the dispersant and continue stirring for at least 5 minutes. Step 7: Prepare carbon paste: Add the sized pitch-based carbon fiber obtained in step 5 to the modified solvent obtained in step 6 under stirring at 300~600r / min, and stir for at least 10min to prevent the pitch-based carbon fiber from agglomerating, so as to obtain a uniform carbon paste. Step 8: Preparation of microwave absorbing slurry: Add water-based organosilicon resin to the carbon slurry obtained in step 7, and add anti-settling agent while stirring. Adjust the slurry viscosity to 40~60cps, and continue stirring for at least 10 minutes until the mixture is uniform to obtain the final water-based asphalt-based carbon fiber microwave absorbing slurry.
7. The application of the water-based bitumen-based carbon fiber microwave absorbing slurry as described in any one of claims 1-5, characterized in that: Absorbing paste used in microwave absorbing cells.